At this configuration (NET_BUFFER 500, NET_PREBUF 0) BASS use continuously a growing amount of RAM. (starting @ ~198 kb till nirvana).The interesting fact on this thing is, if i change the NET_BUFFER from 500 to 1000, memory usage will be continuously the same.

The BASS_StreamCreateURL call will allocate a download buffer (according to the BASS_CONFIG_NET_BUFFER setting) and that then stays the same for the life of the stream, so I'm not sure where that increasing memory usage would be coming from. To make sure it isn't from something else in your app, please see if you can reproduce the problem with the NETRADIO example.